player: Avoid deadlock
player: Avoid deadlock

When the play thread receives an error (ret < 0), it waits for
aoplayCond. But if the buffer is full (decode thread waiting for
aoplayCond), the player deadlocks.

See #672.

gnowxilef/pianobar,gnowxilef/pianobar,gnowxilef/pianobar,gnowxilef/pianobar,gnowxilef/pianobar,gnowxilef/pianobar